Tobacco cleaner and classifier



March 4, 1958 Y L. A, RowELL 2,825,457

TOBACCO CLEANER AND CLASSIFIER Filed July 15, 1953 5 Sheets-Sheet l \q INVENTOQ Loiwvz 71. Pan/Eu.

March 4, 1958 L. A. ROWELL TOBACCO CLEANER AND CLASSIFIER 3 SheetsSheet 2 Filed July 15, 1953 IN WEN TOE E72 Fawwz L. A. ROWELL TOBACCO CLEANER AND CLASSIFIER 3 Sheets-Sheet s INVENTOR .EMQNEE Fan/EM.

March 4, 1958 I Filed July 15, 1953 United States Patent TOBACCG CLEANER AND CLASSIFIER Lorne A. Rowell, Lachine, Quebec, Canada, assignor to Imperial Tobacco Company of Canada Limited, Montreal, Quebec, Canada, a corporation of Canada Application July 15, W53, Serial No. 368,080

12 Claims. (Cl. 209-139) This invention relates to a cleaning and classifying machine which, while capable of moregeneral application, is particularly useful for cleaning and classifying tobacco products such, for example, as a mixture of tobacco strips and stems.

In the present instance, the invention will be described as applied to the cleaning and classifying of mixtures of tobacco strips and stems, but it will be obvious that the novel principles and procedures involved, are applicable, in Whole or in part, to the cleaning and classifying of various other materials.

The term strip is herein used to designate a tobacco leaf, or a part thereof, which has been detached from the stem.

The term clean stems is herein used to designate tobacco leaf stems from which all laminae have been removed.

The term dirty stems is herein used to designate tobacco leaf stems having laminae attached thereto.

The term lamina is herein used to designate a fragment of tobacco leaf attached to a stem.

A salient feature of the invention is the provision of a pneumatic cleaning and classifying machine in which the design and assembly of the component parts is such as to effect a substantial reduction in cost and floor space requirements as compared with previously available installations for doing the same work.

Another feature of the invention is the provision of a pneumatic cleaning and classifying machine in which the cleaning and classifying operations and the conveyance of the classified material from the machine is accomplished by the use of air currents in the absence of mechanical conveying means such as belt conveyors or the like.

Another feature of the invention is the provision of an pneumatic cleaning and classifying machine in which all of the air used for classifying and conveying purposes is supplied by a single fan and, with the exception of a small amount, which is preferably bled oif to maintain a slight negative pressure in the machine, is re-circulated and reused without being discharged to atmosphere.

Another object of the invention is the provision of a cleaning and classifying machine, which is completely pneumatic in operation and in which high velocity jets of air are used in a novel manner in combination with pneumatic classifying chambers and pneumatic conveying systems to effect an exceptional efiicient cleaning and classification of the material being treated.

A further feature of the invention is the provision of a pneumatic cleaning and classifying machine, in which the material being classified is projected into a series of classifying chambers by high velocity jets of air and in which the air jets are efficiently employed in combination with the classifying chambers to free lighter particles of the material being classified from lumps in which such lighter particles are entangled with or entrapped by heavier particles.

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A further feature of the invention is the provisioncf a pneumatic cleaning and classifying machine in which the material being classified is projected into each of a plurality of classifying chambers by high velocity jets of air delivered through suitable jet nozzles, the air thus delivered to the classifying chambers being returned to the suction side of a fan from which this air is again delivered under pressure to the jet nozzles.

A further feature of the invention is the provision o a pneumatic cleaning and classifying machine of the character described, in which asingle fan is employed for supplying the required air to the jet nozzles and to the pneumatic conveying system by means of which the heavier material is delivered from the machine, the ar rangement being such that practically all of the air supplied by the fan for the cleaning and classifying and conveying operations is collected and returned to the suction side of the fan for reuse, thereby eliminating the objectional discharge of tobacco dust laden air into the atmosphere through the use of filters.

A further feature of the invention is the provision of a pneumatic cleaning and classifying machine, of the character described, in which the heavy material is discharged pneumatically from one machine directly into the intake of the next machine, or this material may be conveyed directly through a tobacco thresher and then fed to the next machine by the same pneumatic conveying system, thus permitting a series of cleaning and classifying machines and tobacco threshers to be connected together in line without the use of belt conveyors.

Other characteristic features and advantages of the invention will appear from the following detailed description of the accompanying drawings, in which- Fig. l is a front elevational view of my improved pneumatic cleaning and classifying machine.

Fig. 2 is a side view of the machine shown in Fig. 1.

Fig. 3 is a view partly in vertical section and partly in side elevational of the machine shown in Figs. 1 and 2.

Fig. 4 is a horizontal sectional view taken substantially along the section line 4-4 of Fig. 3, and

Fig. 5 and 6 are enlarged fragmentary detail views.

As shown in these drawings, my improved tobacco" cleaner and classifier comprises a casing 5 provided with a top opening 6 through which the tobacco product to be cleaned and classified is delivered to the upper end of a vertical passage 7 bounded on one side by superimposed inclined pneumatic classifying chambers 8, 9, 10 and 11 and on the three remaining sides by the casing walls 12 and 13 and the wall 14 of a plenum or'pressure tank 15 located within said casing.

The classifying chambers 8, 9, 10 and 11 are open at their upper and lower ends and arranged one directly above the other with the top and bottom walls 16 of each chamber inclined upwardly from the communicating passage 7 to a collecting chamber 18, the latter being bounded on one side by said classifying chambers and on the three remaining sides by the casing walls 12, 13 and 19.

As here shown in Fig. 3 the arrangement of the classifying chambers S, 9, 10 and 11 is such that the bottom wall of each of the chambers d, 9, 10 forms the top wall of the next lower chamber.

The collecting chamber 18 contains a power driven cylindrical screen 2! rotatably mounted therein directly above a hopper 21 through which classified material delivered to chamber 18 is directed into a pneumatic con-' The screen 20 is driven by chain drive 23, speed,

7 reducer 23a and belt drive 23b or by any other suitable 'nism from a motor 51.

' tion by operation of both of saidscrews. V V V The mode of operation of the cleaning and classifying,

' V V I v V V V 7 7V for-n1 of'drivemechanism, from a motor 24 mounted on the top wall 25 of casing S. I I

Classified material which is pneumatically transported through the classif -yin'g chambers 18, as hereinafter de scribed, is projected against the screen 20- and is brushed therefrom into the hopper *2 1 by measles a bi'u sh 26 (Fig. '3) which is; held against said screen with light pres sure by suitable useful applying means such -for example, V t as the, pressure. applying armrlda and spring '27 shown 7 in Fig. 1. I

" agenc of a belt drive 33 or any othersuitableform of V driving means. The pressure side of fan 31 is connected, 7

by airdelivery conduit '34, to the lower portiori'of the 'plenum'or pressure tankJISJ High velocity jets of the,

air thusfsupplied to tank'IS are'deliveredtherefrom to the previously 'mentioned vertical'passage 7 through a 5 series of nozzles 36, 37, 38, 39;, 40; 41,42 and 43'which, V as shown in Fig. 3, constitute part of the wall structure 14 of tank '15 andare arranged one above the other. v. j

The bottom of vertical passage 7 is formed by'a collecting hopper 44 through which material reaching the bottom of said passage is delivered to a verticallyinclined pneumatic conveying conduit 45 through which such material is pneumatically discharged from the machine.

I to the tangential inlet 47, of a centrifugal separator48 in which the solid material delivered through said conduit is separated from the entraining air and discharged through a conventional rotating air-lock outlet 49 forming part of said separator, the rotor of said air-lock being a driven by chain driveSG or other suitable driving mecha- The' pneumatic separator 48 shown in the present instance is of the type including a rotary screen 52 through which the air delivered to the V separator by conduit 45 passes and is thus separated from I the entrained solid material which drops to the air-lock outlet 49. The screen 52 'is'closed at one end anduis driven from the rotor of the air-lock outlet 4h through'a belt drive 54 or other suitable driving means. The other end of screen 52 is open'and is connectedby an airtrecirculating conduit 56 to the previously mentioned air recirculating conduit 30 connected between the suction side of fan 31 of the previously mentioned screen 20.

' eases?- 37 serves to direct the lighter material which slides down the bottomwall 1 60f chamber 8 'baekup intothe air i of the. mixture'and to becarriedlupwardly throughlclassifying'chamber Sto collecting chamber 18.7 The'lighter I materialthus delivered to collecting'chamber i8 is therein machine described herein will be clear f rom the follow;

ing description. 7, V V V a The mixture of loose tobacco strips and tobacco stems below the inlet 6 it is struck b y 'a'high velocity jet of air delivered from pressure tankflS through the nozzle 36'; This high velocity jet of rairisiso directed across passage 7 as to projectall but the very'heavy particles of the mixture into classifying chamber 8. Some of the lighter strip thus projected into chamber '3 is carried therethrough V bythe air current and delivered to colle'cting chamber'isl 5 1 A larger proportion of the material projected into classify- 1 ing chamber 8 lby the air jet delivered through nozzle 36 7 drops onto" the 'bottom'wall'1'6 of said chamber-and slides t down to the mouth of the said chamber where it 'is'struck by a second high' velocity air' jet delivered from pressure tank 15 through nozzle'37.- This secgndhigh velocity air jet is directed against a curved deflecting surface 16;; at; the lower end of bottom wall '16 of classifying chamber, 8 and is deflected upwardly towards the jet deliveredv through nozzle 36, The jet thus delivered through nozgle jet from nozzle 36 where this lightertm'aterial gets a of the'lighter strip to clear itself from the-heavier particles separatedfrom the'air stream by rotary screen 21) and drops through hopper 211 into pneumatic conveying eonj v duit 22 which is connected to a suction fanj;(not shown) 'or other sourceto'f suction entirely separate from the'fan' l 31. Thehe'a'vier material which continues to move'down: wardly in rpassagel7 past classifying chamber 8 carries with it a certain proportion er lighter free strip which is separated from tthers t ems in the classifying chambers 9," 10 and '11 'byrepetitionof the pneumatic procedure de; scribed in connection with separating chamber 8 andis deliveredjtot collecting chamber 18. In this connection 7 it maybe explainedthat the heavier material' andthe The air recirculating conduitst30 and 56 are equipped i with adjustable dampers 57 and 53 for controlling' the flow of air therethrough The'damper 57 may be adjusted through the agency of a belt or chain drive 59 connecting the shaft of the damper to an operating shaft.

60"equippedwith an operating handle 61 The damper 58 'is preferably a conventional type of damper which is rAmfurther adjustable damper indicated at 62 is arentrained {strip which travels downwardly beyond ielassi-l fying chamber 8' is'str'uckby' air jets which are delivered through nozzles 38 and and which actonthe material to efiect a tumbling thereof at'the mouth of the classify;

' ing chamber 9 and to causethe lighter portions of the material to be delivered through. chamber 9 tocollecting chamber 18,

throughinozzles 38 and 39 act onrthe material passing the mouth of the classifying chamber 9 in thesame' manner in which theairrjets delivered throughthe nozzles 36 In other words-the air jets delivered l and 37 "act on the material passing the mouth of: the

ranged in the pressure tank 15 in the inclined position shown in Fig. ,3. This damper may be warped or may be bodilyehifted to diiferent inclined positions by means of two'positioning screws 63 which are rotatably supported by the casing wall 64 in threaded engagement with said damper. Only one screw 63 is shown in the present are employed and are threadedly engaged with-the damper classifying chamber 8. This is also true of the air jets which are delivered through the nozzles 40: and 41 to act on 'thetmaterial passing the mouth of classifyingehamber and the air jets delivered through nozzles 42 'and 43 to act: on the material passing the mouth of the lower-'7 most classifying'ehamber 11. a

The'heavier mate'rial, 'consisting mainlyof clean and f dirty stems which droptto the bottom of passagegj is l delivered through'hopper 44m conduit 45 and is" pneuthe damper 62 to be warped by operation'of either screws 63 or to be moved bodily to difierentpositions of inclinaj V V V g V 'matically conveyed to the separator 48'from which the drawings but it will be understood, that two such screws air separated from such material isreturned through conduit 56 to the suction side of fan' 31 for reuse'together withjthe air which is returned to the suction side of said fan from thescreen 20 arranged in collecting chamber 18.

a sess? effected in the machine are separately conveyed therefrom, the air circuits of the two systems being interconnected so that practically all of the material conveying air passing therethrough is recirculated back to the fan 31 for reuse, thus avoiding the objectionable discharge of relatively large volumes of used tobaccodust laden air to the atmosphere.

The relatively small amount of air bled from the machine through conduit 22 is air which enters the machine through the inlet 6, leakage cracks at the transparent inspection windows 66 and at other points of leakage. It will thus be seen that suction conduit 22 serves to maintain a slight negative pressure in the casing and to change the air in the casing in addition to conveying the cleaning strips from the machine.

Transparent panels 67 are preferably provided at both sides of the machine so that the separating process in the upper parts of the separating chambers 8, 9, and 11 may be observed to facilitate adjustment of the machine. The machine is also provided with suitable doors 68 and 69 to give access to the compartments housing the fan 31 and its operating motor 32.

The adjustable damper 62 located in pressure tank serves a two-fold purpose. It divides the pressure chamber into compartments B and C and creates a pressure differential between these compartments. It also serves to equalise pressures in compartment C' so that substantially uniform velocities are obtained throughout the length of the jets 37 to 43 inclusive, which extend substantially from the wall 12 tothe wall 13 of casing 5. By adjusting damper 62 to vary the opening B at the top of compartment B the air velocity in conduit 45 may be raised or lowered to a considerable extent.

It is important to note here that by appropriate setting of the damper 62 in pressure tank 15 and the damper 57 in air recirculating conduit 30 it is possible to adjust the air velocities in classifying chambers 8, 9, 10 and 11 without appreciably altering the air velocity in conduit 45.

By employing the positioning screws 63 to effect an appropriate twisting or warping of damper 62 it is possible to increase or decrease the effective area of the opening B of compartment B at one side of the pressure tank as compared with the area of said opening at the opposite side of said tank.

Adjustment of damper 57 in air recirculating conduit 30 is normally the only means employed to compensate for different conditions of the product being classified. Partial closure of this damper 57 reduces the air velocity in all of the classifying chambers 8, 9, 10 and 11 whereas wider opening of said damper increases the air velocity in said classifying chambers.

Damper 58 in air recirculating conduit 56 is used fo controlling the velocity in conduit 45 through which material dropping to the bottom of vertical passage 7 is delivered to separator 48. This damper 58 and the damper 62 in tank 15 are normally used only for initial adjustments of the machine to suit the product being treated and should not need to be changed while the machine is in operation.

The various jet nozzles 36 to 43 inclusive are preferably formed and mounted as illustrated in Figures 5 and 6. As here shown each nozzle is formed by upper and lower stream-lined nozzle members 71 and 72 mounted for swinging movement in a vertical plane to vary either the effective area of the nozzles or the direction of the air jets delivered therethrough. The nozzle members 71 and 72 are carried by supporting and adjusting rods 73 which are rotatably mounted in the walls 12 and 13 of casing 5 and are secured in adjusted position by clamping nuts '74. The flow of air from tank 15 through the nozzles 36 to 43 inclusive is stream-lined by means of appropriately curved deflectors 75 carried by the nozzle supporting wall 14 of tank 15. Suitable sealing strips 77 are also clamped to wall 14 in sealing contact with the component members 71 and 72. of. the .nozzles as shown to advantage in Figures. 5 and 6 in order to'confine'the dischargeof airfr'om the tank 15 to the jet passages provided by and between the component nozzle members 71 and 72 of each'nozzlef These sealing members 77 are clamped between clamping plates 78 and opposing portions of the wall 14 of tank 15.

Deflectors 79 are preferably attached to the wall 14 of tank 15 so as to overlie the jet nozzles in the manner shown in Figs. 3 and 6. Certain of these deflectors are provided with attaching flanges which are secured to the wall 14 of tank 15 to provide the previously mentioned clamping plates 78 by means of which certain of the sealing strips 77 are secured in place.

It will be noted that the top portion of each of the classifying chambers extends in a vertical direction. This has the effect of preventing heavier particles which have been given a high initial velocity by the air jet nozzles from escaping from the upper ends of the classifying chamber due to this high initial velocity. Consequently, only that material that can be lifted vertically by the substantially uniform velocity of air in the vertically extending portions of the classifying chambers can escape from the upper ends of said chambers.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pneumatic cleaning and classifying machine of the character described comprising a casing provided with a vertical passage and with an inlet opening through which a descending stream of the material to .be classified is delivered to the upper portion of said vertical passage, a plurality of pneumatic classifying chambers arranged one above the other within said casing at one side of said vertical passage and having their lower inlet end in open communication with said vertical passage, the said classifying chambers being inclined upwardly to terminate in vertically directed open ended discharge outlets arranged in horizontal levels one above the other, a collecting chamber located in the upper portion of said casing above the top level of said vertical passage within which the upper open ends of said classifying chambers terminate, a pressure tank located at the side of said vertical passage remote from said classifying chambers, a plurality of adjustable jet nozzles in the wall of said vertical chamber opposite to the lower openings of said classifying chambers, said nozzles directing high velocity jets of air from the said pressure tank against the stream of material flowing downwardly in said vertical passage, an air impeller having its pressure side connected to the lower portion of said pressure tank to supply compressed air thereto and having its suction side connected to said collecting chamg ber to form a closed air circuit, a screen arranged in said collecting chamber so that the air delivered to the collecting chamber from the classifying chambers is forced-to pass through said screen before being delivered to the suction side of the air impeller, a collecting hopper at the 2. A pneumatic cleaning and classifying machine of the character described comprising a casing provided witha vertical passage and with an inlet opening through which a descending stream of the material to be classified is delivered to the upper portion of said vertical passage, a plurality of pneumatic classifying chambers arranged one above the other within said casing at one side of saidv vertical passage and having their lower inlet ends in open communication with said vertical passage, the said classifying chambers being inclined upwardly to terminate in vertically directed open ended discharge outlets arranged in horizontal levels one above the other, a collecting cham ber located in the upper portion of said casing above the top level or an vrimn passage within which at upper open ends of said classifying chambers terminate, apressur'etank located at one side of said vertical passage re mote fromsaid classifying chambers, a plurality of pairs 1 of jet nozzles through which high'velocity jets of air are Z,delivered from said tank and directed against the down flowing stream of material .to project particles of said material into said classifying chambers so that certain of the particles thus delivered to the classifying chambers are separated from the other particles'and pneumatically'con- 'Yeyed'to and through the discharge openingsof said chain, (hers, each of said classifying 'chambersincluding a bottom. wall having itsupper surface of its lower end portion concavely curved and; the nozzles of eachpair being arranged oneabove the other opposite the inlet opening of one of said classifying chambers with theupper nozzle arranged to direct an-iipper jet stair directly intothe' material receiving space between the top and bottom walls of the classifying ,ehamber and the lower nozzle arranged to a direct a jet of air against the concavely curved surface of the bottom wall of the classifying chamber,- an air impeller having'its pressure side connectedlto' the lower portion of i said pressure tank to supply compressedgair' thereto, and having its suction sideconnected to sai'd'collecting chain her, to form a closed air circuit, a screen arranged in said collecting chamber so that the air delivered to the collecting chamber from the classifying chambers is forced to j V pzlssthrough said screen before being deliveredto the suctionside' of the air impeller, a collecting hopper at the lower end 'of said vertical passagega material separator, a conduit connecting the lower end of said collecting hopper with said material separator, a pressure airpassage from i the pressure side of said air impeller connected to the lower end of said collecting hopper and with said conduit,

and an adjustable damper in said pressure tank dampening the flow. of pressure air, from said air impeller to the upper portion of said pressure tank and to said nozzles.

'3. A pneumatic cleaning and classifying machine of the character described comprising a'casing providedwith'a vertical passage and with an inlet opening through which a jdesce nding stream of the material to be classified is delivered to the upperportion of said; passage, a plurality of pneumatic classifyingjchambers arranged one above the other withinsaid casing and atone side of said vertical 7 I passage, said classifying chambers inclining upwardly from-saidpassage and being open at both ends, a collect.- ing chamber at the upper ends of said classifying chambers and communicating therewith, a pressure tank located at the side of said vertical passage remote from'said classifya ing chambers, a plurality of jet nozzles through which high velocity :jets of air are directed from said pressure tank against the stream of material flowing downwardly in said vertical passage, an air impeller having its pressure side connected to thelower portion of said pressure tank to bottom of said vertical passage is delivered to said conduit.-

"5; A tot-s cleaning jand"classifying machine-as set forth in claim a, includingfanadjustable damper-dividing the lower portion or the pressure chamberinto twosompartments opening into chamber.

6IA tobacco cleaning and classifying machine asfset forth in claim 3, including an adjustable damper dividingi thelower'portion of'the pressure chamber; into twe com- V partments'opening into the upper portion of the pressure chamber, and adjusting screws connected tofsaid damper for effecting warping or' bodily adjustinent thereof.

7. A tobacco cleaning and classifyingmachineasset i forth in claim 3, includinga pneumatic conduitconnected to said collecting chamber tolconvey material therefrom.

V 8. A tobacco cleaning and classifyingmachinerasset forth in claim 3, includingan adjustable damper dividing the lower portion of the pressure damper. intotwocompartments communicating at the upperedge ofithedamper with the space in the upper portioniof said pressurezcham- V i her, saiddam'per' comprising a flat plate extending oblique ly across'the lower? portion of the pressure, chamber and a supported at its lower edge and adjusting screws extending inwardly through a wall of said casing and having threaded engagement with said damper plate, saida'djusting-screws being positioned adjacent opposite. endslof said plate.

9. A pneumatic cleaning and classifying machine; of'

the 'character'described comprising a-plur-ality of=superimposed inclined pneumatic classifying chamhers hav- 2 ing inlet "openings at theirlowercnds and discharge 7 openings at their upper ends, means, forconducting aj." flowing stream of material to be classified downwardly past the inletopenings of said classifying chambers,fa pressure tank, positioned oppositeandin spaced rela tion to the lower ends of said classifying chambers, a

plurality of'pairs" of jet nozzles through which high velocity jets of air are deliver-edffrom saiditankf'and directeel against down flowingstreamiof material tofproject particles of said material into saidlclassifying-c ambers so that certain of wtheparticles thus delivereagmme separating chambers are separated from the btherlpan, 1 7 ticles and pneumatica'llyiconveyed'to andthroug'h ,thetdis-j charge openings of'saidchambers, each of said classify; ing chambers including a bottemnau having the upper surfaces of its lower end portion 'c'oncavelyqcurved and,

the nozzles of each'pair being arrangedione abovethe other opposite the inlet opening of one of'saidclassifying 4. A tobacco cleaningrand classifying machine as set forth in claim 3, including a separator to which the other end of said pneumatic conveying conduit is connected, airrecirculating conduit means through which air, delivered to said separator by said pneumaticair conveying conduit is returned to' the suction side of said air impellerand a, screen arranged in said separator so that the air delivered to the separator from said'conveying conduit isforced to pass through said screen before being returned to the suc* tion side of said air impeller. A

chambers with the-upper nozzle arranged todirect an upper'j'et of airdirectlyint'o the materialfreceiving space between the top and bottom 'walls of the: classifying chant her and the lower nozzle arrangedto direct sister 'air against the concave'ly curved surface of the bottom wall of the classifying chamber, ,an'air impeller havingit's pressure side connected, to the lower port-ionf'of said l pressurechamber, a pneumatic conveyin'g'conduitjto which material passing downwardlybeyond the lowermost of said classifying chambers is delivered, said pneumatic conveying conduit having one end connected to the pressure side of 'said'air impeller toreceive compressed air therefrom and-an adjustable damper arranged in said pressure tankfand dividing the lower portion thereof; into two compartments; opening into the upper portion I f said pressure'tank. i

10. A tobacco cleaning and classifying machine'of the I character described comprising'a casing provided with i a vertical passage and an inlet openingthrough which a descending stream delivered to the upper end of said passage; a plurality of pneumatic classifying chambers arranged one above the other within the said 'casingfand at one side of'said vertical passage, a'pressurei chamber located atthe opp'osite side of said passage, air impellerhavingitsdis 7 charge side connected to 'thelowerporti0n of said pressure chamber, and a' plurality ofadjustable' jetnozzles through which high velocity jets of air are delivered from said pressnre'chamber across said vertical: passage and the pe rportien; of the pre sure of the material to be, classified is into said classifying chambers, each of said jet nozzles being formed by upper and lower nozzle members mounted for swinging movement in a vertical plane to vary either the effective area of the nozzles 01' the direction of the air jet delivered therethrough.

11. A tobacco cleaning and classifying machine as set forth in claim 10, in which the component nozzle members of each nozzle are carried by supporting and adjusting rods rotatably mounted in opposite walls of said casing.

12. A tobacco cleaning and classifying machine as set forth in claim 10, including curved deflectors arranged within the pressure tank to provide stream-lined con- '10 verging approach passages through which air is directed from the tank to and through the nozzle openings afforded by the upper and lower nozzle members of each nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 393,411 Willis Nov. 27, 1888 902,474 Conner Oct. 27, 1908 1,706,787 Kellie Mar. 26, 1929 1,846,209 Kramer Feb. 23, 1932 2,658,617 Rowell Nov. 10, 1953 

